Typically, a vehicle has a suspension system to help cushion the ride to the driver and passengers and to help the vehicle safely negotiate corners. The components of this suspension system can include the following: Tires, which deform to absorb bumps and return to previous size; Springs, which cushion impact; Shock absorbers located between the axle or frame or struts as part of the axle assembly to dampen the effect of impact, and; Bushings which are placed between the junctions of the above components usually made of rubber.
A problem that can face vehicles is that all bumps or deflections in the road should be absorbed to avoid affecting the driver and passengers. Those bumps or deflections are usually absorbed by the tires. The rubber tire under pressure is able to deform and rebound after encountering small deflections. However, when the same vehicle enters a turn, the tire gives or deforms as pressure is applied to it from the body of the vehicle above. The higher the tire from the rim, the greater the deformation in a turn and, consequently, the more the vehicle rolls to the outside, regardless of the stiffness of the rest of the suspension.
A stiff suspension has been the first traditional choice in an effort to control the roll of the vehicle in a turn. But as explained above, if for example, the tire deforms three inches in a 50 MPH turn, the vehicle will roll to the outside the same three inches, even if the shock or strut does not give at all. In order to counteract this roll, a specifically designed tire, a so-called “low profile” tire can be used. This tire has very little height from the rim. Therefore, there is very little deformation of the tire in a turn and the vehicle corners much better. However, when the vehicle encounters a small deflection the tire does not deform as much as regular tires and the passengers and driver can be significantly jarred by even the smallest bumps.
Even with the use of a stiff suspension and low profile tires, a vehicle can still roll to the outside on the turn because of the bushings used. The conventional bushings are typically made of rubber and there may be two to three bushings for each unit of suspension, each being one half of an inch thick or more. The presence of bushings can allow for a further roll of about one to one and a half an inches depending upon the stiffness (durometer reading) of the bushings, as well as the stiffness of the suspension and the type of tires.
In U.S. Pat. Nos. 5,979,616; 5,971,115; 5,529,153 and 5,437,354, which are incorporated herein by reference, various tilt control systems are described, which allow further softness in the ride of the vehicle in straight line driving but which provide for increased stiffness of the shock/strut/spring portion of the suspension system when the vehicle enters a turn. However, with any of the systems, even if the shock absorber is very firm, the vehicle can still roll in a turn due to the deformation of the tire and the compression of the bushing. In testing, the roll from these two components on a sport utility vehicle was equivalent to approximately 2 to 3 inches to the outside on a turn.
To compensate for such roll, some prior art has described using a technique of manufacturing the bushings with an air space inside the hard rubber. In this fashion, there is a soft component to the bushing as the air bubble inside is compressed and a hard component as the rubber outside resists compression. However, when the vehicle enters a turn there still will be roll from the bushings very quickly from compression of the air and then further from compression of the rubber.